Predictive maintenance aims to sustain the availability of equipment and avoid catastrophic failures, which may cause severe consequential damage to other components of the equipment before the equipment can be shut down. The avoidance of catastrophic failures often reduces the number of components to be replaced. Predictive maintenance is further beneficial in that equipment down time can be predicted and scheduled. Thus, unscheduled down time can be minimised and delays that may be incurred due to procurement of spare parts can be avoided.
Rotating and reciprocating machinery represent very commonly found types of equipment found in industry and it is for this reason that extensive work has been conducted on techniques to aid predictive maintenance programs on such equipment, including vibration analysis, infra-red thermography and oil analysis.
Two known techniques used in vibration analysis include Time Synchronous Averaging (TSA) and Order Tracking. Both techniques are used in conjunction with a conventional Fast Fourier Transform (FFT) to produce a frequency spectrum of the vibration data for analysis to detect vibration signatures indicative of actual or potential fault conditions.
Various vibration analysis techniques are well documented and have a proven record in predicting catastrophic failures. However, an area that has attracted little attention is that of the analysis of frequently reversing drives, particularly such as found in rotating and reciprocating machinery. No techniques are currently known for the successful analysis of equipment vibrations whilst that equipment is accelerating or decelerating and for differentiation between vibration signatures in the forward and reverse directions. One reason is that system dynamics change with speed, direction, and more importantly, with load. Another reason for the limited analysis of frequently reversing drives is that the period during which the equipment runs at a constant speed is normally insufficient for vibration analysis to be performed.
A need thus exists for a vibration analysis technique that can be applied to frequently reversing, rotating, reciprocating and cyclic machinery. Draglines, shovels, winders and cranes, are just some examples of rotating and reciprocating machinery that would clearly benefit from a successful predictive maintenance strategy incorporating advanced vibration analysis techniques such as TSA and Order Tracking.